Determination of structural parameters of uranyl ions complexed with organic acids using EXAFS

• Published in: Journal of alloys and compounds Vol. 271; pp. 123 - 127
• Main Authors: Denecke, M.A, Reich, T, Bubner, M, Pompe, S, Heise, K.H, Nitsche, H, Allen, P.G, Bucher, J.J, Edelstein, N.M, Shuh, D.K
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 12.06.1998
• Subjects: ABSORPTION SPECTROSCOPY; Bidentate coordination; Carboxylate ions; Dibenzoatodioxouranium(VI); Extended X-ray absorption fine structure spectroscopy; MOLECULAR STRUCTURE; Monodentate coordination; ORGANIC ACIDS; RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; Sodium triacetatodioxouranium(VI); URANYL COMPLEXES; X-RAY SPECTROSCOPY; Bidentate coordination; Monodentate coordination; Extended X-ray absorption fine structure spectroscopy; Carboxylate ions; Dibenzoatodioxouranium(VI); Sodium triacetatodioxouranium(VI)
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(98)00038-3

Two compounds of known crystal structure, sodium triacetatodioxouranium(VI), Na[UO 2(CH 3COO) 3], and dibenzoatodioxouranium(VI), UO 2[C 6H 5(COO)] 2, were studied by uranium L III-edge extended X-ray absorption fine structure, EXAFS, spectroscopy to differentiate between bidentate and monodentate coordination of carboxylate ions on the basis of the uranium–equatorial oxygen, O eq, bond lengths. Bidentate coordination can be verified by detecting carboxyl carbon atoms and the neighboring distal carbon atom of the organic rest. In contrast, EXAFS spectra for monodentate carboxylate complexes show no evidence of carbon atoms beyond the O eq coordination shell. The mode of coordination was determined by EXAFS analysis for solid uranyl complexes with humic, methoxybenzoic, and salicylic acids. A correlation between the U L III-edge X-ray absorption near-edge structure, XANES, and the U–O eq bond distance according to the relationship Δ E· R(O eq) 2=constant was observed. For the samples studied, the constant was determined to be 197±8 eV Å 2.